The Rangers’ inability to lock down games is a manifestation of their failure to lock into the defensive structure that led the club to the second-best record in the NHL last season.

For the most part, it has been amble-scramble in their own end, with defensemen and forwards alike chasing, and often caught out of position. There were games last season when the Blueshirts spent an inordinate amount of time in the defensive zone, sometimes pinned for a shift at a time, but they were able to keep the puck to the outside, on the perimeter, while denying seams.

This year, seams are splitting. The Rangers are leaving wide swatches of ice in their own end. The shut-down guys on defense haven’t been sharp or stiff enough. The neutral zone play and forecheck are deficient as well. And as a result — bang! — a three-goal, third-period lead erased within a stretch of 10:33 by the Bruins in Boston on Tuesday and a two-goal lead surmounted within a span of 6:56 in the second period by the Islanders at the Garden on Thursday.

“The defensive structure is definitely a concern. It has to be better,” Ryan Callahan told The Post following Thursday’s 4-3 shootout loss. “We know that the foundation works. It was the basis of our success last year, but we haven’t been the same tight unit that we need to be.

“We need to close out better and take away time and space. And we’re certainly not blocking shots as well. We have to get back to the basics. We have to get back to our game.”

It might be easier said than done, however, in a season in which practice time is at a premium because of the compressed schedule. And with coach John Tortorella believing devoutly that rest and replenishment are more critical than practice time, the Rangers continue to receive scheduled days off, including yesterday.

“It’s tough but it’s across the board,” Tortorella said on Thursday when asked about the lack of practice time. “We’re trying to do an extraordinary amount of tape work. That’s how we’re trying to correct. That’s what we’re hammering away at.”

The Rangers had better be able to hammer out a defensive structure. If not, it will be amble-scramble all the way for a team that probably can’t thrive freelancing.